完成对话
A: How was your vacation, Fred?
B: ____ .
A: ____ ?
B: I went to the U.S. with my parents.
A: Cool! ____  in the U.S.?
B: First we went to Los Angeles(洛杉矶). My uncle lives there. Then we went to New York to see my cousin.
A: ____ ?
B: It was a little warm but sunny.
A: Did you see any movie stars in Los Angeles?
B: No, but I saw Tom Cruise in New York. He was at a restaurant! I got his autograph.
A: Wow! That’s great!  What else did you do in New York?
B: Hmm…Oh yeah, I also went to Central Park.____ there! .

如果﹣4x^ay^a+1与mx⁵y^b﹣1的和是3x⁵yⁿ，求（m﹣n）（2a﹣b）的值．

下列各句中加线词的解释，全部正确的一项是（    ）

空气中能供给动植物呼吸的气体是（　　）